The cell membrane is a flexible structure that surrounds both plant and animal cells. The arrangement of molecules within the cell membrane makes it semi-permeable. That is, the cell membrane allows some substances to easily diffuse into and out of the cell, but it prevents the diffusion of other substances. Plant and animal cell diagram

The cell wall is a rigid structure that surrounds plant cells. The materials found in the cell wall protect the plant cells and give plants structural support.

Why are small quantities of chlorofluorocarbons so harmful to the ozone layer? a. the chlorofluorocarbons act like ultraviolet radiation causing large amount of ozone to be produced. b. the chlorine from the chlorofluorocarbons reacts with free molecules of oxygen causing a stop in ozone production c. free oxygen atoms can replace the chlorine in chlorine monoxide, releasing a free atom of chlorine which can then recombine with an oxygen atom in ozone, destroying more ozone. d. chlorofluorocarbons absorb ultraviolet radiation, preventing the formation of ozone select the best answer from the choices provided

2. in dragons, a gene on chromosome 1 codes for wing color and a gene on chromosome 2 codes for body color. draw out the stages of meiosis for these two chromosomes from a dragon that is heterozygous for both traits. define your alleles. what are all the possible allele combinations of the gametes produced?

An ecologist studied the same species of deer during the summer and the winter. she noticed that during the summer, when there was plenty of food, the deer were energetic and playful. however, during winter when food was scarce, the deer moved more slowly and did not run unless they needed to escape a predator. which scientific fact is best supported by her observations?